1. Field of the Invention
This invention relates to an image forming apparatus in which an electrostatic latent image formed on a photoreceptor is developed into a toner image, and the toner image is transferred onto a copy sheet transported along a transport path, and to a copy sheet guide structure for use in such image forming apparatus.
2. Description of the Background Art
Generally, there have been known electrostatic type image forming apparatuses such as facsimile machine and copying machine comprising a charger, a developing unit, a transfer unit, and a cleaning unit that are arranged in the periphery of a photoreceptor, an exposure unit for exposing an image on the photoreceptor, and a copy sheet transport mechanism for supplying and transporting copy sheets.
The image forming apparatuses are operated such that the photoreceptor, the exposure unit, and the copy sheet transport mechanism are driven synchronously to sequentially perform operations of charging the photoreceptor, exposing an image on the photoreceptor, developing the exposed image, and transferring the image on a copy sheet transported from the copy sheet transport mechanism.
Further, the image forming apparatus are operated such that the copy sheet for image transfer is dispensed from a paper cassette by the copy sheet transport mechanism, and transported to a fixing unit along a specified transport path via the transfer unit, and the cleaning unit removes toner residues on the photoreceptor after the image transfer.
The conventional copy sheet transport mechanism used in the above image forming apparatus has adopted a guide structure constructed in the following manner. Specifically, the guide structure comprises plural (e.g., two) guide plates fixed on a main body of the apparatus to define a transport path therebetween. After one of the guide plates has been fixed on the apparatus main body by fastening means (e.g., screw), the other guide plate is fixed on the apparatus main body by fastening means as opposed to the already fixed guide plate apart by a certain clearance. Thereby, a guide space for guiding a copy sheet is defined between the two guide plates. The guide space partially constitutes the transport path.
The above conventional guide structure in which the guide plates are fixed on the apparatus main body by fastening means deteriorates workability in assembling the parts and becomes one of the factors for cost rise in producing the apparatus.
The conventional guide structure has another drawback. The finished state of the guide space, i.e., the result as to whether the guide space is shaped into an exact size, greatly affects smooth guiding of copy sheet (hereinafter also referred to as "sheet guiding ability"). The above conventional arrangement of defining the guide space by fixing the two guide plates individually on the apparatus main body makes it difficult to define the guide space with high precision, hence hindering improvement of the sheet guiding ability.